package 南京国睿信维;

public class Q_12 {
    static void fun(){
        A a = new A();
        A b = new B();
        A c = new C();//儿子 转成 爹
        C c1 = (C)c;//爹 才能 转 儿子
    }

    public static void main(String[] args) {
        fun();
    }
}

class A{

}
class B extends A{

}
class C extends B{

}